In recent years, rechargeable electric storage devices, such as battery cells (lithium-ion battery cells, nickel-metal-hydride battery cells and the like) and capacitors (electric double layer capacitors and the like) have been adopted as power sources of vehicles (e.g., automobiles, two-wheeled motor vehicles and the like) and various equipment (mobile terminals, notebook-size personal computers and the like). This type of electric storage device is provided with an electrode assembly including a positive electrode plate and a negative electrode plate insulated from each other, a case for housing the electrode assembly, and external terminals arranged on an outer surface of the case and electrically connected to the electrode assembly.
This type of electric storage device is provided with a gas exhaust valve for releasing the internal pressure of the device by means of rupture or cleavage if the internal pressure exceeds a certain value. The gas exhaust valve is arranged on a cover plate along with the external terminals (Japanese Patent Laid-Open Nos. 2010-244898 and 2011-192547). Accordingly, constituents of a gas discharged from the gas exhaust valve or an electrolytic solution discharged therefrom as the gas is discharged may adhere to the external terminals or the vicinity thereof when the gas exhaust valve operates. If the constituents of the gas or the electrolytic solution adhere to the external terminals or the vicinity thereof, an unfavorable situation, such as corrosion, occurs due to a potential difference.